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312            MOEPHOLOGY AND EVOLUTION
nerve is given off at the level of the fifth and sixth thoracic nerves, and the small splanchnic nerve separates off at the level of the diaphragm. The usual rarai com-municantes and aortic nerves are given off. In the Gorilla there are eleven thoracic ganglia, and the great splanchnic nerve comes from the sixth to twelfth ganglia; the whole arrangement, in fact, is more complex than in the Chimpanzee and somewhat simpler than in Man.
Abdominal Sympathetic.—In the Chimpanzee the number of ganglia does not correspond always to that of the lumbar nerves; in one animal there were four left and two right ganglia. They give off the following branches in order from above downwards (fig. 53):—
1.  Communicating to the inferior mesenteric plexus (LM.P.) and renal plexus (E.P.).
2.  Eami communicantes to the lumbar nerves (E.G.).
3.   Ovarian plexus (O.P.).
4.   Communicating to the aortic plexus (A.P.).
5.  Inferior mesenteric plexus.
•    6. Hypogastric nerves (H.N.).
7. External iliac nerves.
The sacral ganglia give rami communicantes to the sacral nerves and hsemorrhoidal and vesical plexuses. Filaments also get into the genital plexuses.
VAGUS AND SYMPATHETIC PLEXUSES.
In all Apes and Man the pharyngeal plexus is formed by branches of the glosso-pharyngeal, vagus and sympathetic nerves.
Cardiac Plexus (fig. 52).—This plexus consists of superficial and deep parts communicating with one another. Their component nerves are :—